kbuild: factor out genksyms command from cmd_gensymtypes_{c,S}

The genksyms command part in cmd_gensymtypes_{c,S} is duplicated.
Factor it out into the 'genksyms' macro.

For the readability, I slightly refactor the arguments to genksyms.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

scripts/Makefile.build

@@ -125,13 +125,14 @@ cmd_cpp_i_c       = $(CPP) $(c_flags) -o $@ $<
 $(obj)/%.i: $(src)/%.c FORCE
 	$(call if_changed_dep,cpp_i_c)
 
+genksyms = scripts/genksyms/genksyms		\
+	$(if $(1), -T $(2))			\
+	$(if $(CONFIG_MODULE_REL_CRCS), -R)	\
+	$(if $(KBUILD_PRESERVE), -p)		\
+	-r $(or $(wildcard $(2:.symtypes=.symref)), /dev/null)
+
 # These mirror gensymtypes_S and co below, keep them in synch.
-cmd_gensymtypes_c =                                                         \
-    $(CPP) -D__GENKSYMS__ $(c_flags) $< |                                   \
-    scripts/genksyms/genksyms $(if $(1), -T $(2))                           \
-     $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
-     $(if $(KBUILD_PRESERVE),-p)                                            \
-     -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
+cmd_gensymtypes_c = $(CPP) -D__GENKSYMS__ $(c_flags) $< | $(genksyms)
 
 quiet_cmd_cc_symtypes_c = SYM $(quiet_modtag) $@
 cmd_cc_symtypes_c =                                                         \
@@ -344,11 +345,7 @@ cmd_gensymtypes_S =                                                         \
     $(CPP) $(a_flags) $< |                                                  \
      grep "\<___EXPORT_SYMBOL\>" |                                          \
      sed 's/.*___EXPORT_SYMBOL[[:space:]]*\([a-zA-Z0-9_]*\)[[:space:]]*,.*/EXPORT_SYMBOL(\1);/' ; } | \
-    $(CPP) -D__GENKSYMS__ $(c_flags) -xc - |                                \
-    scripts/genksyms/genksyms $(if $(1), -T $(2))                           \
-     $(patsubst y,-R,$(CONFIG_MODULE_REL_CRCS))                             \
-     $(if $(KBUILD_PRESERVE),-p)                                            \
-     -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
+    $(CPP) -D__GENKSYMS__ $(c_flags) -xc - | $(genksyms)
 
 quiet_cmd_cc_symtypes_S = SYM $(quiet_modtag) $@
 cmd_cc_symtypes_S =                                                         \